Antibodies are proteins produced by the immune system from the body's stores of
immunoglobulin protein. A healthy immune system produces antibodies in an effort
to protect us. The immune system cells produce antibodies when they react with
foreign protein antigens, such as infectious organisms, toxins and pollen. At
any given time, the body has a large surplus of antibodies, including specific
antibodies that target thousands of different antigens. High antibody levels are
a sign of a healthy, normal-functioning immune system.|
Antibodies are normally produced in response to a foreign protein or substance
within the body, typically a pathogen, which is a infectious organism. Normally,
the immune system is able to recognize and ignore the body's own cells and to
not overreact to non-threatening substances in the environment, such as foods.
Sometimes, however, the immune system ceases to recognize one or more of the
body's normal constituents as "self," leading to production of autoantibodies.
These autoantibodies attack the body's own cells, tissues, and/or organs,
causing inflammation and damage.
Active and Passive Antibodies
Active immunization entails the introduction of a foreign molecule into the
body, which causes the body itself to generate immunity against the target. This
immunity comes from the T lymphocytes (T cells) and the B lymphocytes (B cells)
with their antibodies. Vaccines are concentrations of infectious agents that are
treated usually with heat or chemicals that render the organism impotent or
incapable of causing infection. The vaccine with then trick the immune system
into reacting and actively producing antibodies against the infectious organism.
Active immunization can occur naturally when a person comes in contact with, for
example, a microbe. If the person has not yet come into contact with the microbe
and has no pre-made antibodies for defense (like in passive immunization), the
person becomes immunized. The immune system will eventually create antibodies
and other defenses against the microbe. The next time, the immune response
against this microbe can be very efficient; this is the case in many of the
childhood infections that a person only contracts once, but then is immune.
Passive immunization is where pre-synthesized elements of the immune system are
transferred to a person so that the body doesn't need to produce these elements
itself. Currently, antibodies can be used for passive immunization. This method
of immunization begins to work very quickly, but it's short lasting, because the
antibodies are naturally broken down, and if there are no B cells to produce
more antibodies, they will disappear. Passive antibodies are concentrated
antibodies given in certain vaccines. Passive vaccines are given in cases in
which there is not time for our immune system to produce antibodies after
IgA, IgM, and IgG Antibodies
Immunoglobulins (Ig) are antibodies and there are five major classes of
antibodies: Immunoglobulin A (IgA), immunoglobulin G (IgG), immunoglobulin D
(IgD), immunoglobulin M (IgM), and immunoglobulin E (IgE). Normally, the body
contains ample amounts of each of these immunoglobulins, which are available for
our body's needs for antibody production.
||IgG is the most abundant of the classes of immunoglobulins.
It's the antibody for viruses, bacteria, and anti-toxins and
found in most tissues and plasma.
||IgM is the first antibody present in an immune response.
||IgA is an early antibody for bacteria and viruses. It's
found in saliva, tears, and all other mucous secretions.
||IgD activity is not well understood.
||IgE is present in the respiratory secretions. It's an
anti-body for parasitic diseases, Hodgkin's disease, hay
fever, atopic dermatitis, and allergic asthma).
All antibodies are made by B cells. Any disease that harms the development or
function of B cells will cause a decrease in the amount of antibodies produced.
Since antibodies are essential in fighting infectious diseases, people with
immunoglobulin deficiency syndromes become ill more often. However, the cellular
immune system is still functional, so these patients are more prone to infection
caused by organisms usually controlled by antibodies. Most of these invading
germs (microbes) make capsules, a mechanism used to confuse the immune system.
In a healthy body, antibodies can bind to the capsule and overcome the
bacteria's defenses. The bacteria that make capsules include the streptococci,
meningococci, and Haemophilus influenza.
Upon exposure to infectious organisms or vaccines, our immune systems quickly
produce IgM and IgA antibodies, which are the earliest antibodies seen after
infection or vaccination. Within weeks, the immune system begins to produce IgG
antibodies. IgA and IgM antibodies are short acting and break down within a few
weeks to months. IgG antibodies are long lasting, in most cases lasting for
In testing for infection or in diagnosing autoimmune conditions, tests for both
IgM and IgG antibodies are often used. For instance, in suspected celiac
disease, patients are tested for IgM and IgA gliadin antibodies. IgE antibodies
develop during allergic responses and parasitic infections. Levels of IgE
antibodies to specific allergens are used to diagnose allergic conditions.
Because allergies stimulate the immune response, high levels of IgE tend to
worsen or exacerbate symptoms in people who have autoimmune disorders. For
instance, in patients with Graves' disease, higher levels of IgE are seen in
people who have the worst symptoms or the most severe cases.
Immunoglobulin deficiency syndromes are a group of disorders that involve
defects of any component of the immune system or a defect of another system that
affects the immune system, leading to an increased incidence or severity of
infection. In these disorders, specific disease fighting antibodies
(immunoglobulins such as IgG, IgA, and IgM) are either missing or are present in
reduced levels. Children who have immunodeficiency syndromes may be subject to
infection, diseases, disorders, or allergic reactions to a greater extent than
individuals with fully functioning immune systems.
When the immune system is weak and ineffective, it reacts inappropriately. When
the immune system erroneously reacts to the protein components of our body’s own
tissues and cells, it produces autoantibodies. Autoantibodies that persist
contribute to autoimmune disease development. Specific autoantibodies occur in
specific autoimmune diseases.
The causes of autoantibody production are varied and not well understood. It's
thought that some autoantibody production is due to a genetic predisposition
combined with an environmental trigger, such as a viral illness or a prolonged
exposure to certain toxic chemicals. There is generally not a direct genetic
link however. While families may be susceptible to autoimmune conditions,
individual family members may have different autoimmune disorders, or may never
develop an autoimmune condition. Researchers believe that there may also be a
hormonal component as many of the autoimmune conditions are much more prevalent
in women of childbearing age.
Autoantibodies as Markers of Disease
Certain antibodies, such as the anti-nuclear antibodies (ANA), which include a
number of different subtypes, are seen in many different autoimmune disorders.
ANA can also be seen in low titers in people free of disease who show evidence
of autoimmunity but no signs of disease.
With multiple sclerosis (MS) there are currently not any autoantibody markers
that are known. The hope is to find such markers so those with clinical signs
and symptoms of MS can have specific tests for autoantibodies to help in the